JP7487633B2 - Distributed Power Systems and Power Conditioners - Google Patents

Description

The present invention relates to a distributed power supply system and a power conditioner.

In recent years, distributed power systems such as photovoltaic power generation systems and storage battery systems have been attracting attention (for example, Patent Document 1). In a distributed power system, DC power generated by a distributed power generation device is converted to AC power by a power conditioner, and the converted AC power is supplied to a load (including self-consumption) via a grid.

Japanese Patent No. 3656556

In a distributed power system, when there is a fluctuation in the energy consumed by the load or a fluctuation in the power generated by the distributed power source, it is conceivable that a reverse power flow from the load to the grid will occur. In order to suppress the reverse power flow, it is conceivable to stop the power conditioner and suppress the supply of power generated by the power generation device to the load. However, in such a case, the power generated by the power generation device will not be used effectively. Therefore, it is conceivable to provide a changeover switch for each load that can switch the connection destination of the load to either the grid or the power conditioner, and to control the changeover switch so that a reverse power flow does not occur. However, in such a case, a control device that switches the switch in response to the load fluctuation is required. It is conceivable that such a control device will be large and costly.

The present invention was made in consideration of the above-mentioned circumstances, and its purpose is to provide a technology that can easily suppress reverse power flow from the load to the grid and supply as much of the power generated by the distributed power source to the load as possible, even when there is a fluctuation in the energy consumed by the load or a fluctuation in the power generated by the distributed power source.

To solve the above problems, the present invention adopts the following configuration.

That is, a distributed power system according to one aspect of the present invention is a distributed power system including a power generation device that generates DC power, and a power conditioner that converts the DC power generated by the power generation device into AC power, the power conditioner being electrically connected to a three-wire commercial power system that supplies power to a load that is a power supply target, the distributed power system including a plurality of the power conditioners each having a control unit, a first CT input circuit that is connected to two or more wires of the three-wire commercial power system and measures the direction and magnitude of the current in each of the two wires, and a second CT input circuit that is provided in each of the two wires and measures the direction and magnitude of the current in each of the two wires. a voltage input circuit for measuring a voltage; and a disconnection device for disconnecting a plurality of the power conditioners from the three-wire commercial power system, the power conditioner including an inverter circuit for converting power generated by the power generation device into AC power and outputting the AC power so that the phase of the power generated by the power generation device is synchronized with the phase of power supplied from a commercial power source to the three-wire commercial power system, an output current meter for detecting the magnitude of the current of the AC power output from the inverter circuit, and a second CT input circuit for inputting a detection signal detected by the output current meter to the control unit. a first CT input circuit, a voltage input circuit, an output current measuring instrument, and a second CT input circuit, and a power supply circuit, the first CT input circuit, a voltage input circuit, an output current measuring instrument, and a second CT input circuit, and the control unit receives signals from the first CT input circuit, the voltage input circuit, the output current measuring instrument, and the second CT input circuit, and controls the inverter circuit to adjust the magnitude of the AC power flowing from the inverter circuit to the three-wire commercial power system when the power supplied to the load from the three-wire commercial power system is equal to or lower than a predetermined power, The power conditioners are gradually disconnected from the three-wire commercial power system within a predetermined period from the time when it is determined that the power supplied from the system to the load is equal to or less than a second predetermined power, and the disconnecting device disconnects the power conditioners from the three-wire commercial power system all at once when it is determined that the power supplied from the three-wire commercial power system to the load is equal to or less than the second predetermined power after the predetermined period has elapsed, and the first CT input circuit and/or the voltage input circuit are arranged outside the power conditioners and connected to the control unit.

According to this configuration, the first CT input circuit is arranged outside the power conditioner, and the direction and magnitude of the current of each of the two wires can be input to the control unit of the power conditioner as a detection signal. Also, the voltage input circuit can be arranged outside the power conditioner, and the voltage of each of the two wires can be input to the control unit of the power conditioner as a detection signal. Note that the power may be calculated outside the power conditioner based on the current measured in the first CT input circuit arranged outside and/or the voltage measured by the voltage input circuit arranged outside, and the calculated power may be input to the control unit of the power conditioner. Therefore, the power conditioner is prevented from limiting the magnitude of the current and the magnitude of the voltage that can be detected by the first CT input circuit and the voltage input circuit. Therefore, according to this configuration, it is possible to measure high voltage and extra high voltage power. Therefore, this configuration can be applied to a wider range of systems.

Furthermore, with this configuration, when the power supplied to the load from the three-wire commercial power system is equal to or less than a predetermined power, the magnitude of the AC power output from the inverter circuit can be adjusted to a smaller value. This control easily suppresses reverse power flow from the load to the system. Furthermore, when the adjustment amount of the magnitude of the AC power output from the inverter circuit is changed according to the input signals from the first CT input circuit, the voltage input circuit, the output current meter, and the second CT input circuit, the adjustment amount does not need to be reduced more than necessary. Therefore, the power generated in the power generation device can be supplied to the load as much as possible while easily suppressing reverse power flow.

In a distributed power system consisting of multiple power conditioners, it is possible to exchange information such as output power, fault information, and operating status through communication between the power conditioners. Then, it is possible that one power conditioner monitors the reverse current and transmits the monitoring information to the other power conditioners, and each power conditioner adjusts the power supplied to the grid to prevent reverse current based on the monitoring information. However, with such a method, it is considered difficult to adjust the power supplied to the grid quickly. Therefore, when reverse current occurs due to fluctuations in energy consumption in the load or sudden fluctuations in the power generated by the power generation device, in a distributed power system consisting of multiple power conditioners, it is considered that all the power conditioners are temporarily disconnected from the grid by gate blocking or grid-connection relay disconnection. However, such a response is considered to cause a large degree of loss of power generated by the power generation device.

On the other hand, according to this configuration, even if the energy consumption in the load or the power generated by the power generation device fluctuates suddenly and the reverse power flow cannot be eliminated by simply adjusting the power supplied from each power conditioner to the grid, the magnitude of the AC power supplied from the inverter circuit to the grid can be adjusted by gradually disconnecting each power conditioner from the grid. Thus, the reverse power flow is eliminated. Furthermore, while eliminating the reverse power flow in this way, all the power conditioners are not disconnected from the grid at the same time, so that the power generated in the power generation device can be supplied to the load as much as possible.

Furthermore, according to this configuration, if the reverse power flow is not eliminated even when the power conditioners are disconnected from the grid in stages, the multiple power conditioners are disconnected from the grid all at once after a predetermined period of time has elapsed. This type of distributed power system reliably eliminates reverse power flow even when the fluctuations in the energy consumed by the load or the fluctuations in the power generated by the distributed power source are so rapid that the reverse power flow cannot be eliminated by simply shutting down the power conditioners in stages.

In the distributed power system according to one aspect of the present invention, the control unit may have a determination unit that determines whether or not to disconnect the multiple power conditioners from the three-wire commercial power grid, and the determination unit may determine whether or not to disconnect the multiple power conditioners from the three-wire commercial power grid based on an average value of a value related to a current flowing through the three-wire commercial power grid from the time of determination to a predetermined past time.

When the fluctuation of the energy consumption in the load or the fluctuation of the power generated in the distributed power source is rapid, the current flowing in the system may momentarily become a reverse flow even if the current is a forward flow. In such a case, it is considered that a reverse flow is occurring in the system, and the multiple power conditioners are gradually disconnected from the three-wire commercial power system. However, according to this configuration, the determination unit determines whether or not to disconnect the multiple power conditioners from the system based on the average value of the value related to the current flowing in the system from the time of determination to a predetermined past time. Therefore, even if the current flowing in the system is a steady forward flow and momentarily becomes a reverse flow, the determination unit is prevented from erroneously determining that a reverse flow is occurring in the system. Therefore, in such a case, it can be said that the disconnection of the power conditioner is prevented, and the power generated in the power generation device is supplied to the load as much as possible. Conversely, even if the current flowing in the system is a steady reverse flow and momentarily becomes a forward flow, the determination unit is prevented from erroneously determining that a forward flow is occurring in the system. Therefore, in such cases, the power conditioner's connection to the grid is suppressed, and the constantly occurring reverse power flow is eliminated.

The distributed power supply system according to the above aspect includes a power supply device that generates DC power, and a power conditioner that converts the DC power generated by the power supply device into AC power, the power conditioner being electrically connected to a three-wire commercial power system that supplies power to a load that is a power supply target. The distributed power supply system includes a plurality of the power conditioners each having a control unit, a first CT input circuit that is connected to two or more wires of the three-wire commercial power system and measures the direction and magnitude of the current in each of the two wires, and a second CT input circuit that is provided in each of the two wires and measures the direction and magnitude of the current in each of the two wires. and a voltage input circuit for measuring the voltage of each of the first and second lines, wherein the power conditioner further includes an inverter circuit for converting power generated by the power generation device into AC power and outputting the AC power so that the phase of the power generated by the power generation device is synchronized with the phase of power supplied from a commercial power source to the three-wire commercial power system, an output current meter for detecting the magnitude of the current of the AC power output from the inverter circuit, and a second CT input circuit for inputting a detection signal detected by the output current meter to the control unit, and the control unit further includes a first CT input circuit for inputting a detection signal detected by the output current meter to the control unit, a signal based on a current measured in a CT input circuit and/or a voltage measured in the voltage input circuit is input, and the control unit receives signals from the first CT input circuit, the voltage input circuit, the output current meter, and the second CT input circuit, and controls the inverter circuit to adjust a magnitude of the AC power flowing from the inverter circuit to the three-wire commercial power system when power supplied from the three-wire commercial power system to the load is equal to or less than a predetermined power, and the control unit gradually reduces outputs of the multiple power conditioners within a second predetermined period from a time point when it is determined that the power supplied from the three-wire commercial power system to the load is equal to or less than a third predetermined power, and when it is determined that the power supplied from the three-wire commercial power system to the load is equal to or less than the third predetermined power after the second predetermined period has elapsed, a second disconnection device collectively disconnects the power conditioners from the three-wire commercial power system, and the first CT input circuit and/or the voltage input circuit are disposed outside the power conditioners and connected to the control unit.

According to this configuration, the first CT input circuit is arranged outside the power conditioner, and the direction and magnitude of the current of each of the two wires can be input to the control unit of the power conditioner as a detection signal. Also, the voltage input circuit can be arranged outside the power conditioner, and the voltage of each of the two wires can be input to the control unit of the power conditioner as a detection signal. Note that the power may be calculated outside the power conditioner based on the current measured in the first CT input circuit arranged outside and/or the voltage measured by the voltage input circuit arranged outside, and the calculated power may be input to the control unit of the power conditioner. According to this configuration, the magnitude of the current and the magnitude of the voltage that can be detected by the first CT input circuit and the voltage input circuit are prevented from being limited by the power conditioner. Therefore, according to this configuration, it is possible to measure high voltage and extra high voltage power. Therefore, this configuration can be applied to a wider range of systems.

Furthermore, with this configuration, when the power supplied to the load from the three-wire commercial power system is equal to or less than a predetermined power, the magnitude of the AC power output from the inverter circuit can be adjusted to a smaller value. This control easily suppresses reverse power flow from the load to the system. Furthermore, when the adjustment amount of the magnitude of the AC power output from the inverter circuit is changed according to the input signals from the first CT input circuit, the voltage input circuit, the output current meter, and the second CT input circuit, the adjustment amount does not need to be reduced more than necessary. Therefore, the power generated in the power generation device can be supplied to the load as much as possible while easily suppressing reverse power flow.

In addition, with this configuration, the magnitude of AC power supplied from the inverter circuit to the grid can be adjusted by gradually lowering the output of each power conditioner. This eliminates reverse power flow. Furthermore, while eliminating reverse power flow in this way, the output from all power conditioners is not simultaneously reduced, so it can be said that the power generated in the power generation device is supplied to the load as much as possible.

Furthermore, according to this configuration, if the reverse power flow is not eliminated even when the output of the power conditioner is gradually reduced, the multiple power conditioners are collectively disconnected from the grid after the second specified period has elapsed. This distributed power system reliably eliminates the reverse power flow even when the fluctuation in the energy consumed by the load or the fluctuation in the power generated by the distributed power source is rapid and the reverse power flow cannot be eliminated by gradually reducing the output of the power conditioner. Furthermore, since the output of the power conditioner is gradually reduced during the second specified period, it can be said that the power generated by the power generation device is supplied to the load as much as possible.

In the distributed power system according to the above aspect, the control unit has a second determination unit that determines whether or not to reduce the output of the multiple power conditioners, and the second determination unit may determine whether or not to reduce the output of the multiple power conditioners based on an average value of a value related to a current flowing through the three-wire commercial power system from the time of determination to a predetermined time in the past.

When the fluctuation of the energy consumption in the load or the fluctuation of the power generated in the distributed power source is rapid, the current flowing in the grid may momentarily become a reverse flow even if the current is a forward flow. In such a case, it is determined that a reverse flow is occurring in the grid, and the output of the multiple power conditioners may be reduced. However, according to this configuration, the second determination unit determines whether or not to reduce the output of the multiple power conditioners based on the average value of the value related to the current flowing in the grid from the time of determination to a predetermined past time. Therefore, even if the current flowing in the grid is a steady forward flow and momentarily becomes a reverse flow, the second determination unit is prevented from erroneously determining that a reverse flow is occurring in the grid. Therefore, in such a case, it can be said that the reduction in the output of the power conditioner is suppressed, and the power generated in the power generation device is supplied to the load as much as possible. Conversely, even if the current flowing in the grid is a steady reverse flow and momentarily becomes a forward flow, the second determination unit is prevented from erroneously determining that a forward flow is occurring in the grid. Therefore, in such a case, the output of the power conditioner is reduced, and the steadily occurring reverse power flow is eliminated.

In addition, a power conditioner according to one aspect of the present invention is a power conditioner that converts DC power generated by a power generation device into AC power, and is electrically connected to a three-wire commercial power system that supplies power to a load that is a power supply target, and is equipped with a control unit having a determination unit that determines whether to disconnect a plurality of the power conditioners from the three-wire commercial power system, an inverter circuit that converts the power generated by the power generation device into AC power and outputs the AC power so that the phase of the power generated by the power generation device is synchronized with the phase of the power supplied from a commercial power source to the three-wire commercial power system, an output current meter that detects the magnitude of the current of the AC power output from the inverter circuit, and a second CT input circuit that inputs a detection signal detected by the output current meter to the control unit, and the control unit is connected to two or more wires of the three-wire commercial power system and measures the direction and magnitude of the current in each of the two wires, and/or a current measured in a first CT input circuit that is provided in each of the two wires and detects the direction and magnitude of the current in each of the two wires. A signal based on the voltage measured in a voltage input circuit that measures the voltage of each of the two wires is input, and the control unit receives signals from the first CT input circuit, the voltage input circuit, the output current meter, and the second CT input circuit, and controls the inverter circuit to adjust the magnitude of the AC power flowing from the inverter circuit to the three-wire commercial power system when the power supplied to the load from the three-wire commercial power system is equal to or less than a predetermined power, and the determination unit determines that the multiple power conditioners will be gradually disconnected from the three-wire commercial power system within a predetermined period when the power supplied to the load from the three-wire commercial power system is equal to or less than a second predetermined power, and the determination unit determines that the multiple power conditioners will be collectively disconnected from the three-wire commercial power system when the power supplied to the load from the three-wire commercial power system after the predetermined period has elapsed is equal to or less than the second predetermined power, and the control unit is connected to the first CT input circuit and/or the voltage input circuit arranged externally.

Further, a power conditioner according to one aspect of the present invention is a power conditioner that converts DC power generated by a power generation device into AC power, and is electrically connected to a three-wire commercial power system that supplies power to a load that is a power supply target, and includes: a control unit having a second determination unit that determines whether to reduce an output of a plurality of the power conditioners; an inverter circuit that converts power generated by the power generation device into AC power and outputs the AC power so that the phase of the power generated by the power generation device is synchronized with the phase of power supplied from a commercial power source to the three-wire commercial power system; an output current meter that detects the magnitude of the current of the AC power output from the inverter circuit; and a second CT input circuit that inputs a detection signal detected by the output current meter to the control unit, and the control unit receives a current measured in a first CT input circuit that is connected to two or more wires of the three-wire commercial power system and that measures the direction and magnitude of the current in each of the two wires, and/or a current measured in a first CT input circuit that is provided for each of the two wires and that detects the direction and magnitude of the current in each of the two wires. a signal based on a voltage measured in a voltage input circuit that measures the voltage of each of the first CT input circuit, the voltage input circuit, the output current meter, and the second CT input circuit is received by the control unit, and when the power supplied from the three-wire commercial power system to the load is equal to or less than a predetermined power, the control unit controls the inverter circuit to adjust a magnitude of the AC power flowing from the inverter circuit to the three-wire commercial power system; the second determination unit determines that outputs of the plurality of power conditioners will be reduced in a stepwise manner within a second predetermined period from a time point when it is determined that the power supplied from the three-wire commercial power system to the load is equal to or less than a third predetermined power; and when it is determined that the power supplied from the three-wire commercial power system to the load is equal to or less than the third predetermined power after the second predetermined period has elapsed, the second determination unit determines that outputs of the plurality of power conditioners will be reduced collectively; and the control unit is connected to the first CT input circuit and/or the voltage input circuit that are arranged externally.

The means for solving the above problems in the present invention can be used in combination as much as possible.

According to the present invention, even if there is a fluctuation in the energy consumed by the load or in the power generated by the distributed power source, it is possible to easily suppress reverse power flow from the load to the grid and supply as much of the power generated by the distributed power source as possible to the load.

FIG. 1 shows a schematic configuration of a distributed power supply system in this application example. FIG. 2 shows an example of an outline of a distributed power supply system according to the first embodiment. FIG. 3 shows an example of an operation flow of the distributed power supply system. FIG. 4 shows an example of the change over time in the grid power and an example of the change over time in the output control target value of each power conditioner. FIG. 5 shows an example of another operational flow of the distributed power system. FIG. 6 shows a schematic configuration of a distributed power supply system according to a first modified example. FIG. 7 shows a schematic configuration of a distributed power supply system according to a second modified example. FIG. 8 shows an overview of a distributed power generation system according to a third modified example.

§1 Application Examples Application examples of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a distributed power system 1 in this application example. In FIG. 1, the distributed power system 1 includes a plurality of photovoltaic power generation devices 20 and a plurality of power conditioners 10 that convert DC power generated in each of the photovoltaic power generation devices 20 into AC power. The plurality of power conditioners 10 are connected to a commercial power system 5 of a commercial power source. A load 2 is also connected to the commercial power system 5. In other words, the AC power output from the power conditioner 10 is supplied to the load 2 and consumed by the facility. The power generated in the photovoltaic power generation devices 20 may be sold.

Here, it is considered that reverse power flow occurs in the commercial power system 5 when, for example, the energy consumed in the load 2 fluctuates abruptly, or when the illuminance at the location where the photovoltaic power generation device 20 is installed fluctuates abruptly due to abrupt changes in the illuminance, etc. In this case, the distributed power system 1 determines whether the current flowing through the commercial power system 5 is greater than a reverse power relay (RPR) detection level. Then, when it is determined that the current flowing through the commercial power system 5 is smaller than the RPR detection level, the operation of the multiple power conditioners 10 is gradually stopped. By such an operation, the reverse power flow is eliminated. In addition, since all the power conditioners are not simultaneously disconnected from the system, it can be said that the power generated in the photovoltaic power generation device 20 is supplied to the load 2 as much as possible. The RPR detection level is an example of the "second predetermined power" of the present invention. In addition, the second predetermined power may be a value obtained by adding a margin to the RPR detection level.

§2 Configuration example [Hardware configuration]
Next, an embodiment of the present invention will be described in detail with reference to the drawings. In this embodiment, a three-wire commercial power system is exemplified as the commercial power system 5, and a load 2 is connected independently between the U phase and the neutral wire O, and a load 3 is connected independently between the W phase and the neutral wire O. The system may be single-phase or three-phase.

Figure 2 shows an example of the outline of the distributed power system 1 in the first embodiment. The distributed power system 1 in the first embodiment includes, for example, a plurality of photovoltaic power generation devices 20 and a power conditioner 10 that is electrically connected to each of the plurality of photovoltaic power generation devices 20 and converts the power generated in each of the photovoltaic power generation devices 20 into AC power. Among the power conditioners 10, the Master power conditioner is designated as 10a, and the other power conditioners are designated as Slave power conditioners (10b, 10c, ...). The distributed power system 1 also includes a communication cable 22 that connects the power conditioners (10a, 10b, 10c, ...) to each other and enables CAN (Control Area Network) communication between the power conditioners (10a, 10b, 10c, ...). The distributed power system 1 also includes connection lines 17, 18, and 19 that connect each of the power conditioners (10a, 10b, 10c, etc.) to the commercial power grid 5.

The power conditioner 10 includes a power conversion unit 13. The power conversion unit 13 is an inverter circuit that converts the power generated by the solar power generation device 20 into AC power having a phase synchronized with the phase of the power supplied to the loads 2 and 3 by the commercial power system 5. The input side of the power conversion unit 13 is connected to the output side of the solar power generation device 20, and the output side of the power conversion unit 13 is connected to a signal output unit 16. This signal output unit 16 is connected to the commercial power system 5 via connection lines 17, 18, and 19. Here, the power conversion unit 13 is an example of an "inverter circuit" of the present invention.

The power conditioner 10 also includes a control unit (MPU) 12 that issues commands to the power conversion unit 13 to control the output power of the power conditioner 10, an output CT (current transformer) 14 that detects the magnitude of the output current of the power conversion unit 13, and a CT input circuit (AD converter) 15c that inputs the detection signal of this output CT 14 to the control unit 12. The output CT 14 is provided between the power conversion unit 13 and the signal output unit 16. Here, the control unit 12 is an example of the "control unit" of the present invention. The output CT 14 is an example of the "output current measuring instrument" of the present invention. The CT input circuit 15c is an example of the "second CT input circuit" of the present invention.

The distributed power system 1 also includes system CTs (current transformers) 6a, 6b as detection means for detecting the direction and magnitude of the current flowing between the commercial power system 5 and the loads 2, 3, and CT input circuits (AD converters) 15a, 15b that input detection signals of the system CTs 6a, 6b to the control unit 12, both located outside the power conditioner 10. The distributed power system 1 also includes voltage input circuits 35a, 35b that input the voltage of the commercial power system 5 (system voltage) as a detection signal to the control unit 12, both located outside the power conditioner 10 and on the connection lines 17-19 between the power conditioner 10 and the commercial power system 5.

Note that the power applied to the loads 2 and 3 from the commercial power system 5 (one example of the "signal based on the current measured in the first CT input circuit and the voltage measured in the voltage input circuit" of the present invention) may be calculated outside the power conditioner 10 from the current detected in the system CTs 6a and 6b and the CT input circuits 15a and 15b, and the voltage detected in the voltage input circuits 35a and 35b, and the calculated power may be input to the control unit 12. Alternatively, either the system CTs 6a and 6b and the CT input circuits 15a and 15b or the voltage input circuits 35a and 35b may be provided outside the power conditioner 10. Then, from either the current detected in the system CTs 6a, 6b and the CT input circuits 15a, 15b, or the voltage detected in the voltage input circuits 35a, 35b, the power applied to the loads 2, 3 from the commercial power system 5 (an example of the "signal based on the current measured in the first CT input circuit or the voltage measured in the voltage input circuit" of the present invention) may be calculated outside the power conditioner 10, and the calculated power may be input to the control unit 12.

The distributed power system 1 also includes a reverse power relay 47 on the connection lines 17-19 arranged outside the power conditioner 10. The reverse power relay 47 includes a changeover switch that switches the power conditioner 10 between parallel-off and parallel-on with respect to the commercial power system 5. The reverse power relay 47 also includes a timer 48 that measures time, and can operate the changeover switch when the time measured by the timer 48 reaches a predetermined time. Here, the CT input circuits 15a and 15b are an example of the "first CT input circuit" of the present invention. The voltage input circuits 35a and 35b are an example of the "voltage input circuit" of the present invention. The reverse power relay 47 is also an example of the "disconnection device" of the present invention.

In the following description, the control unit 12 of the Master power conditioner 10a will be referred to as the control unit 12a, and the control unit 12 of the Slave power conditioner 10b will be referred to as the control unit 12b. Similarly, the reverse flow prevention control unit 122 provided in the control unit 12a will be referred to as the reverse flow prevention control unit 122a, and the reverse flow prevention control unit 122 of the control unit 12b will be referred to as the reverse flow prevention control unit 122b. The symbols of the other functional components will also be expressed according to the same rules.

(Details of the control unit 12a)
Next, the control unit 12a of the master power conditioner 10a will be described in detail. The control unit 12a controls the power conversion unit 13a so that no reverse power flow occurs from the loads 2 and 3 to the commercial power system 5. More specifically, the control unit 12a includes a power flow direction determination unit 123a. The power flow direction determination unit 123a stores in the memory unit 11a (described later) a value (hereinafter referred to as a control deviation) relating to the difference between the system power at the power receiving point where the system CT (6a, 6b) is provided and the RPR detection level, which is a system power obtained using a current detection signal input from the CT input circuit (15a, 15b) and a voltage detection signal input from the voltage input circuit (35a, 35b). The RPR detection level is a threshold value below which the output power from the power conditioner 10 is disconnected from the commercial power system 5 (described later in detail). This RPR detection level may be, for example, a power value when 5% of the rated power of the power conditioner 10 flows to the reverse flow side from a 0 W state where there is neither reverse flow nor forward flow. Incidentally, the control deviation is expressed, for example, by the following formula (1).
Control deviation [%] = [{(-grid power) - (-RPR detection level)} ÷ Σpower conditioner rating] × 100 [%] - offset ... (1)

As shown in formula (1), the control deviation is the ratio of the difference between the RPR detection level and the grid power to the total value of the rated output power of the power conditioners (10a, 10b, ...) [
%].

The control unit 12a is also connected to a storage unit 11a in which data necessary for the control performed by the control unit 12a is stored. The storage unit 11a is configured to include memory elements such as ROM and RAM. The above-mentioned control deviation is stored in the storage unit 11a. More specifically, the storage unit 11a stores a monitoring period (for example, 6 s) of the grid power for a predetermined period (for example, 500 ms).
The control deviation described above is stored as a divided period deviation Amin[n] (n = 0 to 11) for each divided period into which the power generation time is divided. The power flow direction determination unit 123a then determines whether or not reverse power flow is occurring based on the average value of each past divided period deviation Amin[n] from the present time, which are stored in the memory unit 11a.

The control unit 12a also includes a reverse power flow prevention control unit 122a that refers to the division period deviation Amin [n] stored in the memory unit 11a and calculates the target value of the output power output from the power conversion unit 13a. The calculation of the target value of the output power is performed periodically for each division period (i.e., every 500 ms). The reverse power flow prevention control unit 122a may increase the output control target value by a predetermined increment (predetermined increment: 1% in this embodiment) when, for example, the minimum value of each past division period deviation Amin [n] from the current time point is greater than a predetermined deviation threshold value (1% of the rated output of the power conditioner in this embodiment). Note that when the output control target value is increased by 1% in this manner, the reverse power flow prevention control unit 122a reduces the division period deviation Amin [n] stored in the memory unit 11a by 1%. The reverse power flow prevention control unit 122a may maintain or reduce the output control target value. The determined output control target value is transmitted to each control unit (12b, 12c, ...) of the slave power conditioner (10b, 10c, ...) via the communication cable 22. In the slave power conditioner (10b, 10c, ...), the reverse flow prevention control unit (122b, 122c, ...) of the control unit (12b, 12c, ...) sets the output control target value based on the output control target value received from the master power conditioner 10a so that its own output control target (%) is the same value.

In addition, when the power flow direction determination unit 123a determines that the current flow at the power receiving point where the system CT (6a, 6b) is provided is a reverse current and detects that the magnitude of the current flow is smaller than the RPR detection level, the reverse current prevention control unit 122a determines the time to execute (hereinafter also referred to as gate block) to disconnect each power conditioner (10a, 10b, ...) from the commercial power system 5 (details will be described later). Then, the reverse current prevention control unit 122a transmits information on the period from the current time to the time to execute the gate block (hereinafter referred to as the detection remaining time) to the reverse power relay 47a. In addition, the reverse current prevention control unit 122a also transmits the detection remaining time information to the control units (12b, 12c, ...) provided in each power conditioner (10b, 10c, ...) via the communication cable 22. Then, the reverse power flow prevention control units 122b, 122c, ...) of the control units (12b, 12c, ...) provided in the respective power conditioners (10b, 10c, ...) transmit the received remaining detection time information to the reverse power relays (47b, 47c, ...) provided in the respective power conditioners. Here, the power flow direction determination unit 123a and the reverse power flow prevention control unit 122a are an example of the "determination unit" of the present invention.

The output side of the control unit (12a, 12b, 12c, ...) is connected to a CPU (not shown) provided in the power conversion unit (13a, 13b, 13c, ...). The control unit (12a, 12b, 12c, ...) is equipped with an inverter output control unit (121a, 121b, 121c, ...). The inverter output control unit (121a, 121b, 121c, ...) transmits a signal to the CPU provided in the power conversion unit (13a, 13b, 13c, ...) to control the inverter circuit of the power conversion unit (13a, 13b, 13c, ...) according to the output control target value. The inverter output control unit (121a, 121b, 121c, ...) uses the output current information of the power conversion unit (13a, 13b, 13c, ...) input from the output CT (14a, 14b, 14c, ...) to feedback control the signal input to the inverter circuit of the power conversion unit (13a, 13b, 13c, ...) so that the output current from the power conversion unit (13a, 13b, 13c, ...) approaches the output control target value.

(Operation example 1)
Next, an example of the operation of the distributed power system 1 will be described. Fig. 3 shows an example of an operation flow of the distributed power system 1. Fig. 4 shows an example (Fig. 4(A)) of a change over time in the system power detected at a power receiving point where the system CT (6a, 6b) is provided, and an example (Fig. 4(B)) of a change over time in the output control target value of each power conditioner (10a, 10b, 10c, ...) when the process of the operation flow shown in Fig. 3 is executed.

(S101)
At the timing (t0) for updating the output control target value, each past division period deviation Amin
Assume that the average value of [n] is greater than a predetermined deviation threshold. In such a case, the reverse flow prevention control unit 122a increases the output control target value by 1%. In addition, the determined output control target value is transmitted to each control unit (12b, 12c, ...) of the slave power conditioner (10b, 10c, ...) via the communication cable 22. In the slave power conditioner (10b, 10c, ...), the reverse flow prevention control unit (122b, 122c, ...) sets the output control target value based on the output control target value received from the master power conditioner 10a so that the output control target (%) in the slave power conditioner (10b, 10c, ...) is the same value.

(S102)
In step S102, the inverter output control units (121a, 121b, 121c, ...) increase the output from the power conversion units (13a, 13b, 13c, ...) in accordance with the output control target value determined in step S101 (FIG. 4(B)). Then, the current flow at the power receiving point where the grid CTs (6a, 6b) are provided changes from forward flow to reverse flow. Then, the magnitude of the current at the power receiving point where the grid CTs (6a, 6b) are provided becomes a value smaller than the RPR detection level (FIG. 4(A)).

(S103)
In step S103, the power flow direction determination unit 123a, which monitors the control deviation, detects that reverse power flow is occurring in the grid. The power flow direction determination unit 123a then determines that the average value of each past division period deviation Amin[n] from the current time is smaller than the RPR detection level. Then, the reverse power flow prevention control unit 122a determines the detection remaining time t1 (one example of the "predetermined period" of the present invention), which is the period from the current time until the gate blocking of each power conditioner (10a, 10b, ...) is executed in stages. More specifically, the power flow direction determination unit 123a determines the detection remaining time t1 of the n-th power conditioner 10n as shown in the following formula (2). Note that n may be, for example, 1 to 28.
Remaining detection time t1 = 8 × n + 48 [ms] (2)

The power flow direction determination unit 123a also determines the detection remaining time t2, which is the period until the gate blocking of each power conditioner (10a, 10b, ...) is executed collectively. For example, t2 is set to 400 ms, which is a value obtained by subtracting 100 ms from 500 ms, which is the period during which the power flow at the receiving point where the system CT (6a, 6b) is installed is detected by the power flow direction determination unit 123a and the output control target value is periodically set. Then, the reverse power flow prevention control unit 122a transmits information on the detection remaining times t1 and t2 determined as described above to the reverse power relay 47a in the device itself. The reverse power flow prevention control unit 122a also transmits information on the detection remaining times t1 and t2 to the control units (12b, 12c, ...) provided in each power conditioner (10b, 10c, ...) via the communication cable 22. Then, the reverse power flow prevention control units (122b, 122c, ...) provided in each power conditioner (10b, 10c, ...) transmit the received information on the remaining detection times t1 and t2 to the reverse power relays (47b, 47c, ...) provided in the respective power conditioners.

(S104)
In step S104, the reverse power relays (47a, 47b, 47c, ...) of the respective power conditioners (10a, 10b, 10c, ...) receive the information on the remaining detection times t1 and t2. Then, in the reverse power relays (47a, 47b, 47c, ...), the timers (48a, 48b, 48c, ...) are activated and start measuring time. Then, when the time measured by the timers (48a, 48b, 48c, ...) reaches the received remaining detection time t1, each reverse power relay (47a, 47b, 47c, ...) outputs a stop signal to operate a changeover switch to disconnect the power conditioner (10a, 10b, 10c, ...) connected to itself from the commercial power grid 5. By performing such an operation in each of the power conditioners (10a, 10b, 10c, ...), the multiple power conditioners (10a, 10b, 10c, ...) are disconnected from the commercial power grid 5 in stages. While the power conditioner 10 is disconnected, the reverse power flow prevention control unit 122 of the power conditioner 10 temporarily sets the output control target value to 0. Then, at the next timing t3 at which the output control target value is determined, the disconnection of the power conditioner 10 is released. Then, at the timing t3 at which the disconnection of the power conditioner 10 is released, the reverse power flow prevention control unit 122 of the disconnected power conditioner 10 re-determines the output control target value. At this time, the reverse power flow prevention control unit 122 may apply a rate limit of 1 [%/s] to the increase rate of the output control target value.

If the power flow direction determination unit 123a of the master power conditioner 10a, which monitors the control deviation, determines that the current value flowing to the commercial power grid 5 is greater than the RPR detection level, the stepwise parallel-off is stopped and the power conditioner is connected to the commercial power grid 5. However, the power flow direction determination unit 123a does not determine the current value of each divided period deviation Amin from the present time point in the past.
The connection of the power conditioner to the commercial power grid 5 is determined based on the magnitude relationship between the average value of Amin[n] and the RPR detection level. Therefore, even if the current currently flowing through the grid is greater than the RPR detection level, if the average value of each divided period deviation Amin[n] is smaller than the RPR detection level, the stepwise parallel-off of the power conditioners (10a, 10b, 10c, ...) continues.

(S105)
In step S105, when a predetermined time has elapsed since step S104 and the time measured by the timer 48a reaches the detection remaining time t2, the power flow direction determination unit 123a of the master power conditioner 10a, which monitors the control deviation, determines that the average value of each past division period deviation Amin[n] from the present time is smaller than the RPR detection level. Then, the reverse power relays (47a, 47b, 47c, ...) provided in each power conditioner (10a, 10b, 10c, ...) output a stop signal to operate the changeover switch so as to disconnect the power conditioner 10 connected to the relay. By executing such an operation in each power conditioner (10a, 10b, 10c, ...), the operation of all the power conditioners (10a, 10b, 10c, ...) is stopped simultaneously. Then, at time t4 after a predetermined period of time has elapsed, the gate blocks in all of the power conditioners (10a, 10b, 10c, ...) are released. When the gate blocks in all of the power conditioners (10a, 10b, 10c, ...) are released, the reverse flow prevention control units (122a, 122b, 122c, ...) initialize the output control target value to 0. Then, the reverse flow prevention control units (122a, 122b, 122c, ...) re-determine the output control target value. The reverse flow prevention control units (122a, 122b, 122c, ...) apply a factor of, for example, 10[%/s] to the increase rate of the re-determined output control target value.
s] may be applied. Here, the remaining detection time t2 is an example of the "predetermined period" of the present invention.

Incidentally, when a predetermined time has elapsed from step S104 and the time measured by the timer 48a reaches the detection remaining time t2, if the power flow direction determination unit 123a determines that the average value of each past division period deviation Amin[n] from the current time point is greater than the RPR detection level, the reverse power flow prevention control unit 122a transmits a request signal to the reverse power relay 47a provided in the device itself to request that the timer 48a stop measuring the time. The reverse power flow prevention control unit 122a also transmits the request signal to the control units (12b, 12c, ...) provided in each power conditioner (10b, 10c, ...) via the communication cable 22. Then, the reverse power flow prevention control units (122b, 122c, ...) provided in each power conditioner (10b, 10c, ...) transmit the received request signal to the reverse power relays (47b, 47c, ...) provided in the device itself. In other words, if it is determined that the average value of each past divided period deviation Amin[n] from the present time point is greater than the RPR detection level, gate blocking of all power conditioners (10a, 10b, ...) will not be executed.

(Operation example 2)
FIG. 5 shows an example of another operation flow of the distributed power system 1.

(S201)
In step S201, the power flow direction determination unit 123a of the master power conditioner 10a determines whether or not reverse power flow is occurring based on the average value of each divided period deviation Amin[n] from the present time through the past.

(S202)
In step S202, if it is determined in step S201 that no reverse power flow is occurring in the commercial power system 5, the power flow direction determination unit 123a uses, for example, the minimum value of each past divided period deviation Amin[n] from the present time to determine whether the magnitude of the power value of the forward power flow is greater than a predetermined threshold. Here, the predetermined threshold is a value set by the user to prevent the occurrence of reverse power flow, and is an example of the "predetermined power" of the present invention.

(S203)
In step S203, if it is determined in step S202 that the magnitude of the power value of the forward flow is greater than the predetermined threshold, the reverse flow prevention control unit 122a maintains the current output control target value.

(S204)
In step S204, if it is determined in step S203 that the magnitude of the power value of the forward power flow is equal to or less than a predetermined threshold, the reverse power flow prevention control unit 122a sets a new output control target value by reducing the current output control target value. Here, the new output control target value is determined using a current detection signal input from the CT input circuit (15a, 15b), a voltage detection signal input from the voltage input circuit (35a, 35b), and a detection signal input from the CT input circuit (AD converter) 15c. The new output control target value may be set to a value as large as possible so that reverse power flow does not occur, for example, based on a theoretical formula, know-how, etc. Also, if it is determined in step S201 that reverse power flow is occurring in the commercial power system 5, the reverse power flow prevention control unit 122a sets a new output control target value by reducing the current output control target value.

The updated output control target value is also transmitted to the slave power conditioners (10b, 10c, ...) via the communication cable 22. In the slave power conditioners (10b, 10c, ...), the reverse power flow prevention control units (122b, 122c, ...) set the output control target value based on the command from the master power conditioner 10a so that their own output control targets are the same value.

(S205)
In step S205, the inverter output control units (121a, 121b, 121c, . . . ) reduce the outputs from the power conversion units (13a, 13b, 13c, . . . ) in accordance with the new output control target value determined in step S204.

[Action and Effects]
According to the distributed power system 1 as described above, as shown in steps S204-S205, when the forward flow power supplied from the commercial power system 5 to the loads 2 and 3 is equal to or less than a predetermined threshold, the output from the power conversion unit (13a, 13b, 13c, ...) is reduced. Thus, the reverse flow from the loads 2 and 3 to the commercial power system 5 is easily suppressed. In addition, the new output control target value set in the reverse flow prevention control unit (122b, 122c, ...) is determined using the current detection signal input from the CT input circuit (15a, 15b), the voltage detection signal input from the voltage input circuit (35a, 35b), and the detection signal input from the CT input circuit (AD converter) 15c. Thus, the output from the power conversion unit (13a, 13b, 13c, ...) does not need to be reduced more than necessary. Thus, the power generated in the solar power generation device 20 can be supplied to the load as much as possible while easily suppressing the reverse flow.

Furthermore, according to the distributed power system 1 as described above, even if the energy consumption in the loads 2 and 3 or the power generated by the photovoltaic power generation device 20 fluctuates suddenly and reverse power flow cannot be eliminated by simply adjusting the power supplied to the commercial power grid 5, the reverse power flow can be eliminated by gradually disconnecting the power conditioners from the commercial power grid 5. Furthermore, while eliminating reverse power flow in this way, it is possible to eliminate the reverse power flow by gradually disconnecting the power conditioners from the commercial power grid 5.
. . ) are not disconnected from the grid, it can be said that the power generated in the photovoltaic power generation device 20 is supplied to the loads 2 and 3 as much as possible.

Furthermore, according to the distributed power system 1 as described above, if the reverse power flow is not eliminated even when the power conditioners are disconnected stepwise from the commercial power grid 5 during the remaining detection time t2, after the remaining detection time t2 has elapsed, all the power conditioners (10, 10a, 10b, 10c, ...
) are collectively separated from the commercial power grid 5. In such a distributed power system 1, even if the fluctuation in energy consumption in the loads 2 and 3 or the fluctuation in power generated in the photovoltaic power generation device 20 is rapid and the reverse power flow cannot be eliminated by simply stopping the power conditioner in stages, the distributed power system 1 can reliably eliminate the reverse power flow after the detection remaining time t2 has elapsed. Moreover, since the power conditioner is stopped in stages during the detection remaining time t2, it can be said that the power generated in the photovoltaic power generation device 20 is supplied to the loads 2 and 3 as much as possible.

In addition, if the fluctuation of the energy consumption in the loads 2 and 3 or the fluctuation of the power generated in the photovoltaic power generation device 20 is rapid, the current flowing in the commercial power system 5 may be a forward flow in a moment, even if the current is a forward flow in a steady state. In such a case, according to the above-mentioned distributed power system 1, the power flow direction determination unit 123a determines whether the current flowing in the commercial power system 5 is a forward flow or a reverse flow based on whether the average value of each past division period deviation Amin[n] from the present time is greater than the RPR detection level. Therefore, even if the current flowing in the commercial power system 5 is a forward flow in a steady state and a reverse flow in a moment, the power flow direction determination unit 123a is prevented from erroneously determining that a reverse flow is occurring in the system. Therefore, in such a case, the disconnection of the power conditioner is prevented, and the power generated in the photovoltaic power generation device 20 is supplied to the loads 2 and 3 as much as possible. Conversely, even if the current flowing through the commercial power grid 5 is steadily reverse and momentarily becomes forward, the power flow direction determining unit 123a is prevented from erroneously determining that a forward power flow is occurring in the grid. Therefore, in such a case, the linkage of the power conditioner is suppressed, and the steadily occurring reverse power flow is eliminated.

In step S103, the detection remaining time t1 may be the period from the present time until the output of each power conditioner (10a, 10b, ...) is reduced. The thus determined t1 is transmitted from the reverse current prevention control unit 122a to the reverse current prevention control units (122b, 122c, ...) via the communication cable 22. Then, each of the reverse current prevention control units (122b, 122c, ...) sets a new output control target value by reducing the current output control target value when the time reaches t1 received from the reverse current prevention control unit 122a. Of course, the reverse current prevention control unit 122a also sets a new output control target value by reducing the current output control target value when t1 is reached. Then, the inverter output control units (121a, 121b, 121c, ...) reduce the output from the power conversion units (13a, 13b, 13c, ...) according to the new output control target value. In such a case, the total power supplied from the power conditioner to the load is gradually reduced, and the same effect as above can be achieved. In such a case, the RPR detection level is an example of the "third predetermined power" of the present invention. The power flow direction determination unit 123a and the reverse power flow prevention control unit 122a are an example of the "second determination unit" of the present invention. The reverse power relay 47 is an example of the "second disconnection device" of the present invention. The remaining detection time t1 is an example of the "second predetermined period" of the present invention.

In addition, according to the distributed power system 1 as described above, the grids 6a, 6b and the CT input circuits 15a, 15b are provided outside the power conditioner 10, and the direction and magnitude of the current flowing between the commercial power grid 5 and the loads 2, 3 are input to the control unit 12 of the power conditioner 10 as a detection signal. In addition, the voltage input circuits 35a, 35b are provided outside the power conditioner 10, and the voltage (grid voltage) of the commercial power grid 5 is input to the control unit 12 as a detection signal. Therefore, the magnitude of the current and the magnitude of the voltage that can be detected by the CT input circuits 15a, 15b and the voltage input circuits 35a, 35b are prevented from being limited by the power conditioner 10. Therefore, according to the distributed power system 1 as described above, it is possible to measure high voltage and extra high voltage power. Therefore, the distributed power system 1 can be applied to a wider range of systems.

§3 Modifications Although the embodiment of the present invention has been described above in detail, the above description is merely an example of the present invention in every respect. It goes without saying that various improvements and modifications can be made without departing from the scope of the present invention. For example, the following modifications are possible. In the following, the same reference numerals are used for the same components as in the above embodiment, and the description of the same points as in the above embodiment is omitted as appropriate. The following modifications can be combined as appropriate.

<3.1>
FIG. 6 shows a schematic configuration of a distributed power system 1A according to a first modified example. As shown in FIG. 6, the distributed power system 1A has a series A and a series B. In this modified example, a master power conditioner 10a and a slave power conditioner (10b, 10c, ...) are provided for the series A. In addition, a measurement slave power conditioner 30b and a slave power conditioner (30c, ...) are provided for the series B. The internal configurations of these power conditioners are the same as those shown in FIG. 2.

The Master power conditioner 10a is connected to the commercial power system 5 by connection lines 17, 18, and 19, the Slave power conditioner 10b is connected to the commercial power system 5 by connection lines 17a, 18a, and 19a, and the Slave power conditioner 10c is connected to the commercial power system 5 by connection lines 17b, 18b, and 19b in series A. The measurement Slave power conditioner 30b is connected to the commercial power system 5 by connection lines 37, 38, and 39, and the Slave power conditioner 30c is connected to the commercial power system 5 by connection lines 37a, 38a, and 39a in series B.

The master power conditioner 10a measures the power between the commercial power system 5 and the loads 2 and 3 at the receiving point of series A using system CTs 6a and 6b. The measurement slave power conditioner 30b measures the power between the commercial power system 5 and the loads 32 and 33 at the receiving point of series B using system CTs 36a and 36b.

The Master power conditioner 10a and the measurement slave power conditioner 30b are connected by a communication cable 22 capable of CAN communication. Similarly, the Master power conditioner 10a and each of the slave power conditioners (10b, 10c, ...) and the measurement slave power conditioner 30b and each of the slave power conditioners (30c, ...) are also connected by communication cables 22.

In this modified example, the measurement points are divided into two, for series A and series B, and the combined output power of the Master power conditioner 10a and the Slave power conditioner (10b, 10c, ...) in each series and the measurement Slave power conditioner 30b and the Slave power conditioner (30c, ...) is controlled to be maximum within a range smaller than the RPR detection level. In addition, the contents of the control of the output of each power conditioner in each of series A and series B are the same as those described in the embodiment.

More specifically, in series A, the output control target value in the control of the Master power conditioner 10a is controlled as a controlled amount based on the percentage of the output of each power conditioner when the total rated output of the Master power conditioner 10a and the Slave power conditioner (10b, 10c, ...) is 100%. Then, in the Slave power conditioners 10b and 10c, control is performed so that their own output control target values (%) become the same value based on the command from the Master power conditioner 10a. Also, in series B, the output control target value in the control of the measurement Slave power conditioner 30b is controlled as a controlled amount based on the percentage of the output of each power conditioner when the total rated output of the measurement Slave power conditioner 30b and the Slave power conditioner (30c, ...) is 100%. In the slave power conditioner (30c...), control is performed so that its own output control target value (%) becomes the same value based on commands from the measurement slave power conditioner 30b.

In this modification, when the reverse flow prevention control unit 122a of the Master power conditioner 10a transmits information on the remaining detection times t1 and t2 to the Slave power conditioner 30b and the power conditioners (30c...) connected to the Slave power conditioner 30b (referred to as Slave/Slave power conditioners), the reverse flow prevention control unit 122a transmits the information on the remaining detection times t1 and t2, for example, 48 ms later than when the information is transmitted to the Slave power conditioners (10b, 10c...). By adjusting the timing of transmission of the remaining detection times t1 and t2 in this manner, the Slave power conditioner 30b or the Slave/Slave power conditioner 30c is stopped at the same time as the Master power conditioner 10a, which is the parent, is stopped.
The power conditioners (30c...) are prevented from being stopped. In other words, the stop of the Master power conditioner 10a, which is the parent, and the stop of the Slave power conditioner 30b or the Slave/Slave power conditioner (30c...) are
This will be achieved in stages.

[Action and Effects]
According to the distributed power system 1A as described above, for example, in series A, when the power consumption by the loads 2 and 3 is greater than the output power by the Master power conditioner 10a and the Slave power conditioners (10b, 10c...), and in series B, when the output power by the measurement Slave power conditioner 30b and the Slave power conditioner (30c...) is greater than the power consumption by the loads 32 and 33, it is possible to perform control such as supplying the output power by the measurement Slave power conditioner 30b and the Slave power conditioner (30c...) to the loads 2 and 3. Then, reverse power flow to the commercial power system 5 can be suppressed.

In addition, since the ratio (%) of the total rated output of the multiple power conditioners is used as the control amount, it is possible to use the same algorithm for each power conditioner even if the number of power conditioners increases. In this way, the control according to this embodiment increases the degree of freedom in the system configuration of the distributed power supply system 1A, making it easier to install the distributed power supply system 1A. As a result, it is possible to reduce the introduction cost and effort and promote the spread of distributed power supply systems. In addition, since the ratio (%) of the total rated output of the multiple power conditioners is used as the control amount, appropriate control is possible even if the fluctuations in output power differ for each power conditioner.

<3.2>
FIG. 7 shows a schematic configuration of a distributed power system 1B according to a modified example. As shown in FIG. 7, the commercial power system 5b to which the distributed power system 1B is connected is supplied with power through r-phase, s-phase, and t-phase power lines of a three-phase three-wire system connected to a high-voltage (6,600 V) commercial power source 7. Here, Δ-connections are made between the r-phase and s-phase, between the s-phase and t-phase, and between the s-phase and r-phase. Then, one phase of the high-voltage three-phase power is converted into single-phase low-voltage (200/100 V) power via a transformer 4, and the converted power is supplied to loads 2 and 3. In FIG. 7, the load 2 is connected between the U-phase and the neutral line O of the single-phase three-wire system connected to the transformer 4, and the load 3 is connected between the W-phase and the neutral line O. , and between the power receiving point Rp that receives power from the commercial power source 7 and the transformer 4, a CT 6a that detects the current flowing in the r-phase and a CT 6b that detects the current flowing in the t-line are connected. In addition, a plurality of power conditioners (10a, 10b, 10c, . . . ) are connected to the single-phase three-wire power line connected to the loads 2 and 3.

[Action and Effects]
According to the distributed power system 1B of the second modified example, it is possible to control the output of the solar power generation devices (not shown) connected to each power conditioner (10a, 10b, 10c, ...) to be as high as possible while suppressing the occurrence of reverse power flow from the single-phase three-wire power lines to the r-phase and t-phase of the three-phase three-wire power lines, and it is possible to more efficiently use the power generated by the solar power generation devices.

<3.3>
FIG. 8 illustrates an outline of a distributed power system 1C according to a third modified example. As shown in FIG. 8, the distributed power system 1C shows an example in which a three-phase load 2a and single-phase loads 2 and 3 are connected to a high-voltage distribution line 21. In this modified example, power from the high-voltage distribution line 21 is supplied to the three-phase load 2a and the single-phase loads 2 and 3 in a consumer premises 52a via a cubicle 52b. The configurations of the Master power conditioner 10a and the Slave power conditioners (10b, 10c, ...) are the same as those shown in FIG. 2. The Master power conditioner 10a and the Slave power conditioner (10b, 10c, ...) are the same as those shown in FIG. 2.
The output ends of the system CTs 6a, 6b are connected between the single-phase loads 2, 3 and the cubicle 52b, and the system CTs 6a, 6b are provided at the power receiving point between the high-voltage distribution line 21 and the cubicle 52b.

[Action and Effects]
In the third variant, it is possible to control the output of the solar power generation device (not shown) connected to each power conditioner to be as high as possible while suppressing reverse power flow from the cubicle 52b in the customer premises 52a to the high-voltage distribution line 21, and it is possible to more efficiently utilize the power generated by the solar power generation device.

<Other Modifications>
In the distributed power system 1, a storage battery may be used instead of the slave power conditioner. In the distributed power system 1, the loads 2 and 3 may be, for example, electric vehicles that require charging. In place of the solar power generation device 20, a fuel cell or a gas engine may be used. In the distributed power system 1, the power conditioners (10a, 10b, 10c, ...) do not have to be stopped all at once after the remaining detection time t2. In the distributed power system 1, the power flow direction determination unit 123a may determine whether or not reverse power flow is occurring based on the control deviation at the current time point, rather than the average value of each past division period deviation Amin[n] from the current time point.

The embodiments and variations disclosed above can be combined with each other.

In the following, the components of the present invention will be described with reference to the reference numerals in the drawings in order to make it possible to compare the components of the present invention with the configurations of the embodiments.
<Appendix 1>
A distributed power supply system (1, 1A, 1B, 1C) including a power generation device (20) that generates DC power, and a power conditioner (10, 30) that converts the DC power generated by the power generation device (20) into AC power, the power conditioner (10, 30) being electrically connected to a three-wire commercial power system (5, 5b) that supplies power to a load (2, 2A, 3, 32, 33) that is a power supply target,
A plurality of the power conditioners (10, 30) each having a control unit (12);
a first CT input circuit (15a, 15b) connected to two or more wires of the three-wire commercial power system (5, 5b) and measuring the direction and magnitude of each of the currents in the two wires;
a voltage input circuit (35a, 35b) provided on each of the two wires for measuring the voltage of each of the two wires;
a disconnecting device (47) that disconnects the plurality of power conditioners (10, 30) from the three-wire commercial power system (5, 5b);
The power conditioner (10, 30) is
an inverter circuit (13) that converts the power generated by the power generation device (20) into AC power so as to synchronize the phase of the power generated by the power generation device (20) with the phase of power supplied from a commercial power source to the three-wire commercial power system (5, 5b) and outputs the AC power;
an output current meter (14) for detecting the magnitude of the current of the AC power output from the inverter circuit (13);
a second CT input circuit (15c) that inputs a detection signal detected by the output current measuring device (14) to the control unit (12),
A signal based on a current measured in the first CT input circuit path (15a, 15b) and/or a voltage measured in the voltage input circuit (35a, 35b) is input to the control unit (12),
The control unit (12) controls the first CT input circuit (15a, 15b), the voltage input circuit (35a, 35b), the output current measuring instrument (14), and the second CT input circuit (1
and when the power supplied from the three-wire commercial power system (5, 5b) to the load (2, 2A, 3, 32, 33) is equal to or lower than a predetermined power, controlling the inverter circuit (13) so as to adjust the magnitude of the AC power flowing from the inverter circuit (13) to the three-wire commercial power system (5, 5b);
the disconnection device (47) stepwise disconnects the plurality of power conditioners (10, 30) from the three-wire commercial power system (5, 5b) within a predetermined period from a time point when it is determined that the power supplied from the three-wire commercial power system (5, 5b) to the load (2, 2A, 3, 32, 33) is equal to or less than a second predetermined power,
when it is determined that the power supplied from the three-wire commercial power system (5, 5b) to the load (2, 2A, 3, 32, 33) after the predetermined period has elapsed is equal to or less than the second predetermined power, the disconnection device (47) collectively disconnects the power conditioners (10, 30) from the three-wire commercial power system (5, 5b),
The first CT input circuit (15a, 15b) and/or the voltage input circuit (35a, 35b) are arranged outside the power conditioner (10, 30) and are connected to the control unit (12),
Distributed power system (1, 1A, 1B, 1C).
<Appendix 2>
The control unit (12) has a determination unit (123) that determines whether or not to disconnect the plurality of power conditioners (10, 30) from the three-wire commercial power system,
The determination unit (123) determines whether or not to disconnect the plurality of power conditioners (10, 30) from the three-wire commercial power system (5, 5b) based on an average value of values related to a current flowing through the three-wire commercial power system (5, 5b) from a time point of determination to a predetermined past time point.
A distributed power system (1, 1A, 1B, 1C) as described in appendix 1.
<Appendix 3>
A distributed power system (1, 1A, 1B, 1C) including a power generation device (20) that generates DC power, and a power conditioner (10, 30) that converts the DC power generated by the power generation device (20) into AC power, the power conditioner (10, 30) being electrically connected to a three-wire commercial power system (5, 5b) that supplies power to a load (2, 2A, 3, 32, 33) that is a power supply target,
A plurality of the power conditioners (10, 30) each having a control unit (12);
a first CT input circuit (15a, 15b) connected to two or more wires of the three-wire commercial power system (5, 5b) and measuring the direction and magnitude of each of the currents in the two wires;
a voltage input circuit (35a, 35b) provided on each of the two wires for measuring the voltage of each of the two wires;
The power conditioner (10, 30) is
an inverter circuit (13) that converts the power generated by the power generation device (20) into AC power so as to synchronize the phase of the power generated by the power generation device (20) with the phase of power supplied from a commercial power source to the three-wire commercial power system (5, 5b) and outputs the AC power;
an output current meter (14) for detecting the magnitude of the current of the AC power output from the inverter circuit (13);
a second CT input circuit (15c) that inputs a detection signal detected by the output current measuring device (14) to the control unit (12),
A signal based on a current measured in the first CT input circuit path (15a, 15b) and/or a voltage measured in the voltage input circuit (35a, 35b) is input to the control unit (12),
the control unit (12) receives signals from the first CT input circuit (15a, 15b), the voltage input circuit (35a, 35b), the output current meter (14), and the second CT input circuit (15c), and when the power supplied from the three-wire commercial power system (5, 5b) to the load (2, 2A, 3, 32, 33) is equal to or less than a predetermined power, controls the inverter circuit (13) to adjust the magnitude of the AC power flowing from the inverter circuit (13) to the three-wire commercial power system (5, 5b);
the control unit (12) gradually reduces outputs of the plurality of power conditioners (10, 30) within a second predetermined period from a time point when it is determined that the power supplied from the three-wire commercial power system (5, 5b) to the load (2, 2A, 3, 32, 33) is equal to or less than a third predetermined power,
a second disconnecting device (47) that disconnects the power conditioners (10, 30) from the three-wire commercial power system (5, 5b) all at once when it is determined that the power supplied from the three-wire commercial power system (5, 5b) to the loads (2, 2A, 3, 32, 33) is equal to or less than the third predetermined power after the second predetermined period has elapsed;
The first CT input circuit (15a, 15b) and/or the voltage input circuit (35a, 35b) are arranged outside the power conditioner (10, 30) and are connected to the control unit (12),
Distributed power system (1, 1A, 1B, 1C).
<Appendix 4>
The control unit (12) has a second determination unit (123) that determines whether or not to reduce the output of the multiple power conditioners (10, 30),
The second determination unit (123) determines whether or not to reduce the output of the multiple power conditioners (10, 30) based on an average value of a value related to a current flowing through the three-wire commercial power system (5, 5b) from a time point of determination to a predetermined past time point.
A distributed power system (1, 1A, 1B, 1C) as described in appendix 3.
<Appendix 5>
A power conditioner (10, 30) that converts DC power generated by a power generation device (20) into AC power, the power conditioner (10, 30) being electrically connected to a three-wire commercial power system (5, 5b) that supplies power to a load (2, 2A, 3, 32, 33) that is a power supply target,
a control unit (12) having a determination unit (123) that determines whether or not to disconnect the plurality of power conditioners (10, 30) from the three-wire commercial power system (5, 5b);
an inverter circuit (13) that converts the power generated by the power generation device (20) into AC power so as to synchronize the phase of the power generated by the power generation device (20) with the phase of power supplied from a commercial power source to the three-wire commercial power system (5, 5b) and outputs the AC power;
an output current meter (14) for detecting the magnitude of the current of the AC power output from the inverter circuit (13);
a second CT input circuit (15c) that inputs a detection signal detected by the output current measuring device (14) to the control unit (12);
a signal based on a current measured in a first CT input circuit (15a, 15b) that is connected to two or more wires of the three-wire commercial power system (5, 5b) and measures a direction and magnitude of a current in each of the two wires, and/or a signal based on a voltage measured in a voltage input circuit (35a, 35b) that is provided in each of the two wires and measures a voltage in each of the two wires,
the control unit (12) receives signals from the first CT input circuit (15a, 15b), the voltage input circuit (35a, 35b), the output current meter (14), and the second CT input circuit (15c), and when the power supplied from the three-wire commercial power system (5, 5b) to the load (2, 2A, 3, 32, 33) is equal to or less than a predetermined power, controls the inverter circuit (13) to adjust the magnitude of the AC power flowing from the inverter circuit (13) to the three-wire commercial power system (5, 5b);
the determination unit (123) determines to gradually disconnect the multiple power conditioners (10, 30) from the three-wire commercial power system (5, 5b) within a predetermined period when the power supplied from the three-wire commercial power system (5, 5b) to the load (2, 2A, 3, 32, 33) is equal to or less than a second predetermined power,
when the power supplied from the three-wire commercial power system (5, 5b) to the load (2, 2A, 3, 32, 33) after the predetermined period has elapsed is equal to or less than the second predetermined power, the determination unit (123) determines to collectively disconnect the multiple power conditioners (10, 30) from the three-wire commercial power system (5, 5b);
The control unit (12) is connected to the first CT input circuit (15a, 15b) and/or the voltage input circuit (35a, 35b) arranged externally.
Power conditioner (10, 30).
<Appendix 6>
A power conditioner (10, 30) that converts DC power generated by a power generation device (20) into AC power, the power conditioner (10, 30) being electrically connected to a three-wire commercial power system (5, 5b) that supplies power to a load (2, 2A, 3, 32, 33) that is a power supply target,
A control unit (12) having a second determination unit (123) that determines whether or not to reduce the output of the plurality of power conditioners (10, 30);
an inverter circuit (13) that converts the power generated by the power generation device (20) into AC power so as to synchronize the phase of the power generated by the power generation device (20) with the phase of power supplied from a commercial power source to the three-wire commercial power system (5, 5b) and outputs the AC power;
an output current meter (14) for detecting the magnitude of the current of the AC power output from the inverter circuit (13);
a second CT input circuit (15c) that inputs a detection signal detected by the output current measuring device (14) to the control unit (12);
a signal based on a current measured in a first CT input circuit (15a, 15b) that is connected to two or more wires of the three-wire commercial power system (5, 5b) and measures a direction and magnitude of a current in each of the two wires, and/or a signal based on a voltage measured in a voltage input circuit (35a, 35b) that is provided in each of the two wires and measures a voltage in each of the two wires,
the control unit (12) receives signals from the first CT input circuit (15a, 15b), the voltage input circuit (35a, 35b), the output current meter (14), and the second CT input circuit (15c), and when the power supplied from the three-wire commercial power system (5, 5b) to the load (2, 2A, 3, 32, 33) is equal to or less than a predetermined power, controls the inverter circuit (13) to adjust the magnitude of the AC power flowing from the inverter circuit (13) to the three-wire commercial power system (5, 5b);
the second determination unit (123) determines to gradually reduce outputs of the plurality of power conditioners (10, 30) within a second predetermined period from a time point when it is determined that the power supplied from the three-wire commercial power system (5, 5b) to the load (2, 2A, 3, 32, 33) is equal to or less than a third predetermined power,
the second determination unit (123) determines to collectively reduce outputs of the plurality of power conditioners (10, 30) when it is determined that the power supplied from the three-wire commercial power system (5, 5b) to the load (2, 2A, 3, 32, 33) after the second predetermined period has elapsed is equal to or less than the third predetermined power,
The control unit (12) is connected to the first CT input circuit (15a, 15b) and/or the voltage input circuit (35a, 35b) arranged externally.
Power conditioner (10, 30).

1, 1A, 1B, 1C: Distributed power supply system 2, 2a, 3, 32, 33: Load 4: Transformer 5, 5b: Commercial power system 6a, 6b, 36a, 36b: System CT
10, 30: Power conditioner 11: Memory unit 12: Control unit 13: Power conversion unit 14: Output CT
15: Input circuit 16: Signal output unit 17, 18, 19, 37, 38, 39: Connection line 18: Connection line 19: Connection line 20: Photovoltaic power generation device 21: High voltage distribution line 22: Communication cable 35: Voltage input circuit 47: Reverse power relay 48: Timer 52a: Customer premises 52b: Cubicle 122: Reverse power flow prevention control unit 123: Power flow direction determination unit

Claims (6)

A distributed power supply system including: a power generation device that generates DC power; and a power conditioner that converts the DC power generated by the power generation device into AC power, the power conditioner being electrically connected to a three-wire commercial power system that supplies power to a load that is a power supply target;
A plurality of the power conditioners each having a control unit;
a first CT input circuit connected to two or more wires of the three-wire commercial power system and configured to measure the direction and magnitude of each of the currents in the two wires;
a voltage input circuit provided on each of the two wires for measuring the voltage of each of the two wires;
A disconnection device that disconnects the plurality of power conditioners from the three-wire commercial power system,
The power conditioner comprises:
an inverter circuit that converts power generated by the power generation device into AC power so that the phase of the power generated by the power generation device is synchronized with the phase of power supplied from a commercial power source to the three-wire commercial power system, and outputs the AC power;
an output current meter for detecting a magnitude of the current of the AC power output from the inverter circuit;
A second CT input circuit that inputs a detection signal detected by the output current measuring device to the control unit,
a signal based on a current measured in the first CT input circuit and/or a voltage measured in the voltage input circuit is input to the control unit;
the control unit receives signals from the first CT input circuit, the voltage input circuit, the output current measuring instrument, and the second CT input circuit, and when power supplied from the three-wire commercial power system to the load is equal to or lower than a predetermined power, controls the inverter circuit to adjust the magnitude of the AC power flowing from the inverter circuit to the three-wire commercial power system;
the disconnection device stepwise disconnects the plurality of power conditioners from the three-wire commercial power system within a predetermined period from a time point when it is determined that the power supplied from the three-wire commercial power system to the load is equal to or less than a second predetermined power,
when it is determined that the power supplied from the three-wire commercial power system to the load after the predetermined period has elapsed is equal to or less than the second predetermined power, the disconnection device collectively disconnects the power conditioners from the three-wire commercial power system;
The first CT input circuit and/or the voltage input circuit are arranged outside the power conditioner and connected to the control unit.
Distributed power systems. The control unit has a determination unit that determines whether to disconnect the plurality of power conditioners from the three-wire commercial power system,
The determination unit determines whether to disconnect the plurality of power conditioners from the three-wire commercial power system based on an average value of a value related to a current flowing through the three-wire commercial power system from a time point of determination to a predetermined past time point.
The distributed power system of claim 1 . A distributed power supply system including: a power generation device that generates DC power; and a power conditioner that converts the DC power generated by the power generation device into AC power, the power conditioner being electrically connected to a three-wire commercial power system that supplies power to a load that is a power supply target;
A plurality of the power conditioners each having a control unit;
a first CT input circuit connected to two or more wires of the three-wire commercial power system and configured to measure the direction and magnitude of each of the currents in the two wires;
a voltage input circuit provided on each of the two wires for measuring the voltage of each of the two wires;
The power conditioner comprises:
an inverter circuit that converts power generated by the power generation device into AC power so that the phase of the power generated by the power generation device is synchronized with the phase of power supplied from a commercial power source to the three-wire commercial power system, and outputs the AC power;
an output current meter for detecting a magnitude of the current of the AC power output from the inverter circuit;
A second CT input circuit that inputs a detection signal detected by the output current measuring device to the control unit,
a signal based on a current measured in the first CT input circuit and/or a voltage measured in the voltage input circuit is input to the control unit;
the control unit receives signals from the first CT input circuit, the voltage input circuit, the output current measuring instrument, and the second CT input circuit, and when power supplied from the three-wire commercial power system to the load is equal to or lower than a predetermined power, controls the inverter circuit to adjust the magnitude of the AC power flowing from the inverter circuit to the three-wire commercial power system;
The control unit gradually reduces outputs of the plurality of power conditioners within a second predetermined period from a time point when it is determined that the power supplied from the three-wire commercial power system to the load is equal to or lower than a third predetermined power,
a second disconnecting device that disconnects the power conditioners from the three-wire commercial power system collectively when it is determined that the power supplied from the three-wire commercial power system to the load after the second predetermined period has elapsed is equal to or less than the third predetermined power,
The first CT input circuit and/or the voltage input circuit are arranged outside the power conditioner and connected to the control unit.
Distributed power systems. The control unit has a second determination unit that determines whether to reduce outputs of the multiple power conditioners,
The second determination unit determines whether or not to reduce the output of the plurality of power conditioners based on an average value of a value related to a current flowing through the three-wire commercial power system from a time point of determination to a predetermined time point in the past.
The distributed power system of claim 3 . A power conditioner that converts DC power generated by a power generation device into AC power, the power conditioner being electrically connected to a three-wire commercial power system that supplies power to a load that is a power supply target,
A control unit having a determination unit that determines whether or not to disconnect the plurality of power conditioners from the three-wire commercial power system;
an inverter circuit that converts power generated by the power generation device into AC power so that the phase of the power generated by the power generation device is synchronized with the phase of power supplied from a commercial power source to the three-wire commercial power system, and outputs the AC power;
an output current meter for detecting a magnitude of the current of the AC power output from the inverter circuit;
a second CT input circuit that inputs a detection signal detected by the output current measuring device to the control unit,
a signal based on a current measured by a first CT input circuit that is connected to two or more wires of the three-wire commercial power system and measures a direction and magnitude of a current in each of the two wires, and/or a signal based on a voltage measured by a voltage input circuit that is provided in each of the two wires and measures a voltage in each of the two wires,
the control unit receives signals from the first CT input circuit, the voltage input circuit, the output current measuring instrument, and the second CT input circuit, and when power supplied from the three-wire commercial power system to the load is equal to or lower than a predetermined power, controls the inverter circuit to adjust the magnitude of the AC power flowing from the inverter circuit to the three-wire commercial power system;
the determination unit determines to gradually disconnect the plurality of power conditioners from the three-wire commercial power system within a predetermined period when the power supplied from the three-wire commercial power system to the load is equal to or less than a second predetermined power;
the determination unit determines to collectively disconnect the plurality of power conditioners from the three-wire commercial power system when the power supplied to the load from the three-wire commercial power system after the predetermined period has elapsed is equal to or less than the second predetermined power,
The control unit is connected to the first CT input circuit and/or the voltage input circuit arranged externally.
Power conditioner. A power conditioner that converts DC power generated by a power generation device into AC power, the power conditioner being electrically connected to a three-wire commercial power system that supplies power to a load that is a power supply target,
A control unit having a second determination unit that determines whether or not to reduce the output of the plurality of power conditioners;
an inverter circuit that converts power generated by the power generation device into AC power so that the phase of the power generated by the power generation device is synchronized with the phase of power supplied from a commercial power source to the three-wire commercial power system, and outputs the AC power;
an output current meter for detecting a magnitude of the current of the AC power output from the inverter circuit;
a second CT input circuit that inputs a detection signal detected by the output current measuring device to the control unit,
a signal based on a current measured by a first CT input circuit that is connected to two or more wires of the three-wire commercial power system and measures a direction and magnitude of a current in each of the two wires, and/or a signal based on a voltage measured by a voltage input circuit that is provided in each of the two wires and measures a voltage in each of the two wires,
the control unit receives signals from the first CT input circuit, the voltage input circuit, the output current measuring instrument, and the second CT input circuit, and when power supplied from the three-wire commercial power system to the load is equal to or lower than a predetermined power, controls the inverter circuit to adjust the magnitude of the AC power flowing from the inverter circuit to the three-wire commercial power system;
the second determination unit determines to gradually reduce outputs of the plurality of power conditioners within a second predetermined period from a time point when it is determined that the power supplied from the three-wire commercial power system to the load is equal to or lower than a third predetermined power,
the second determination unit determines to collectively reduce outputs of the plurality of power conditioners when it is determined that the power supplied from the three-wire commercial power system to the load after the second predetermined period has elapsed is equal to or less than the third predetermined power;
The control unit is connected to the first CT input circuit and/or the voltage input circuit arranged externally.
Power conditioner.

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